Generation and power amplification of 1.4-μm ultra-broadband noise-like pulses using a bismuth-doped germanosilicate fiber laser and amplifier

The 1.4–1.5 μm spectral region is attractive for water‑absorption‑related photonic applications and E- and S-band optical communication systems, but suitable silica-compatible gain media remain limited. We developed a single-mode, low-germanium bismuth-doped germanosilicate fiber (BGSF) and used this common fiber platform as the gain medium for both a laser and an amplifier. To our knowledge, this all-fiber laser system provides the first demonstration of ultra-broadband noise-like pulse (NLP) generation and efficient power scaling at 1.4 μm. With a seed power of 13.59 mW, the amplifier delivered an average output power of 103 mW and a pulse energy of 26.30 nJ, corresponding to a 7.6-fold power increase and a slope efficiency of approximately 79 %. The amplified pulse train exhibited a radio-frequency signal-to-noise ratio of 59.72 dB. Meanwhile, the typical dual-scale autocorrelation signature of NLPs was well preserved, whereas the coherent spike width broadened from 284 fs to 553 fs. The amplifier also broadened the 3-dB spectral bandwidth from 9.18 to 13.81 nm and the 10-dB bandwidth from 14.38 to 68.69 nm. At the maximum amplifier pump power of 178 mW, the measured amplified spectral coverage extended from 1400 nm to beyond 1650 nm (20-dB bandwidth > 197.74 nm). These results show that the low-germanium BGSF-based all-fiber laser and amplifier can support ultra-broadband NLP generation and efficient power amplification at 1.4 µm.